Nucleophilic Substitution: Synthesis of N-Butyl Bromide and T-Pentyl Chloride

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Nucleophilic Substitution|
Synthesis of n-Butyl Bromide and t-Pentyl Chloride|
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Jessica|
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Abstract

The synthesis of the alkyl halide n-Butyl Bromide from alcohol is the foundation for the experiment. During the isolation of the n-butyl bromide, the crude product is washed with sulfuric acid, water, and sodium bicarbonate to remove any remaining acid or n-butyl alcohol. The primary alkyl halide halide n-butyl bromide is prepared by allowing n-butyl alcohol to react with sodium bromide and sulfuric acid. The sodium bromide reacts with sulfuric acid to produce hydrobromic acid . Excess sulfuric acid acts to shift the equilibrium and speed up the reaction by producing a higher concentration of hydrobromic acid. The sulfuric acid protonates the hydroxyl group of n-butyl alcohol so that water is displaced instead of the hydroxide ion OH-. The acid also protonates the water as it is produced in the reaction and deactivates it as a nucleophile. Deactivation of water keeps the alkyl halide from being transformed back to the alcohol by nucleophilic attack of water. The reaction of the primary substrate continues via an SN2 mechanism.

Introduction

Halogenoalkanes, also known as haloalkanes or alkyl halides, are organic compounds in which one or more hydrogen atoms in an alkane have been replaced by halogen atoms, fluorine, chlorine, bromine or iodine. In carbon-halogen bond, halogens have significantly greater electronegativities than carbon except iodine. In result, this group is polarized so that the carbon is electrophilic and the halogen is nucleophilic. Halogenoalkanes can be classified depending on the halogen atom position on the chain of carbon atoms. The carbon which is attached with the halogen atom is linked up with only one other alkyl group in primary halogenoalkanes, whereas directly linked up with two and three other alkyl groups in secondary halogenoalkanes and tertiary halogenoalkanes. In some instances, primary halogenoalkanes are counted even though there are no alkyl groups attached to the carbon with the halogen on it. Three characteristics provide important influences on the chemical behavior of halogenoalkanes, these are electronegativity, covalent bond strength, and the relative stability of the corresponding halide anions. Haloalkanes are used in as refrigerants, solvents, blowing agents, aerosol propellants, fire extinguishing media , and in semiconductor device fabrication. One of big consumption of halogenoalkanes is as a raw material to prepare plastics such as PVC from chloroethene and polytetrafluoroethene from tetrafluoroethene. Halogenoalkanes react with lots of compounds resulting in a wide range of different substances. They are useful intermediates in making other organic compounds. 1-Bromobutane, also known as n-butyl bromide is a primary alkyl halide, with the formulaCH3CH2CH2CH2Br . It is colorless liquid, insoluble in water, but soluble in ethanol and ether. Its melting point is 112 C and its boiling point is between 101 and 102 C. It is used as an alkylating agent to introduce the butyl groups to form carbon-carbon bonds in organic synthesis. They are also used as  intermediate to form alkylated amines and alkylated metallic compounds. The end products include pharmaceuticals, insecticides, quaternary ammonium compounds, flavors and fragrances.

Materials and Methods

17.0 grams of sodium bromide was placed in a 100 mL round bottom flask and 17 mL of water and 10.0 mL of n-butyl alcohol was added. The mixture was cooled in an ice bath and 14 mL of concentrated sulfuric acid was slowly added making sure that there was continuous swirling in the ice bath. Several boiling stones were added to the mixture and a reflux apparatus and trap were assembled according to the Pavia text. The mixture was heated to a gentle boil for 60-75 minutes via a heating mantle. For the extraction process the heat source was removed and the apparatus cooled so that the...
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